1. Field of the Invention
This invention relates to a diversity receiver including plural antennas and one receiver so as to switch the antennas in response to their receiving conditions, and thereby suited for use in a car.
2. Description of the Prior Art
An FM receiver mounted in a car or other moving bodies is usually used while the body moves. Therefore, the direction of its antenna always largely changes as compared to a house-use FM receiver, and is apt to disaccord with directions of antennas of broadcasting stations. As the result, it is difficult to block influences by multipath noises.
The receiver of this type is mostly used in a weak electric field because electric field strength for the receiver always varies as the car goes from highways to mountainous places, or from valleys to valleys between tall buildings. Due to this, the receiver must deal with noises intermittently generated within the receiver itself during reception of weak input signals.
One of conventional methods to overcome the abovementioned problem is to change the receiver from stereophonic mode to monoral mode upon reception of weak input signals, or to attenuate high frequency band wave in addition to the foregoing mode changeover. By this method, however, since S/N (signal-to-noise ratio) improvement measure is taken within the receiver to the input signal received by a single antenna, there is accordingly a limit in said improvement.
Another method is to provide two antennas and two tuners, thereby constructing a so-called diversity receiver so as to switch and select the antennas and the tuners in response to the receiving conditions. Although this method is more effective in said S/N improvement than the above-introduced method, however, provision of two tuners causes increase of production cost and space.